As he prepares to make his first NRL appearance in 1680 days this Saturday night, Sonny Bill Williams has indicated that he may be available to play for New Zealand in the end of season World Cup.

Williams, who was not officially due to join Sydney Roosters until today but began training last week, is only contracted until October 31 and there is speculation he will return to Japanese rugby union or box when his NRL commitments finish.

But the 27-year-old dual international told Fairfax Media that he planned to meet with Kiwis coach Stephen Kearney before the NRL season began.

"I have got to catch up with Mooks [Kearney]," Williams said. "His last Test for the Kiwis was my first, and he is a good friend.

"I was supposed to meet him in Brisbane before the fight [against Francois Botha] but it didn't work out. I just said I was busy and he understood. We said we would catch up in Sydney."

Kearney said he hoped to meet with Williams the week before the opening NRL match between the Roosters and South Sydney on March 7.

Williams is also being courted to play for Samoa and he is attracted by the opportunity to play alongside close friend Reni Maitua, who was in his dressing room for the fight with Botha along with their former Bulldogs team-mates Willie Tonga and Nate Myles.

But the chance to add a rugby league World Cup medal to the rugby union version he won with the All Blacks in 2011 would be an attractive lure for him to play for the Kiwis.

If he does, Williams may play a second season for the Roosters but New Zealand rugby union officials are predicting he will return for the 2015 World Cup and the dual international admitted he was tempted by the prospect of representing his country in sevens at the 2016 Olympic Games in Rio.

"To win a gold medal sounds pretty good," he said.

"As a sportsman, if you don't have those sorts of dreams or aspirations then you may as well just stay in bed."

Williams is expected to make his debut for the Roosters in Saturday night's Foundation Cup clash with Wests Tigers after fronting up at his new club just three days after a controversial 10th round win over Botha.

The fight was Williams's sixth and Botha's 61st, and the All Blacks superstar was physically and mentally drained afterwards but he still insisted on attending Roosters training last Monday - although he did not take part in a session until Wednesday.

Those close to him say his return to the NRL was clearly weighing on him during the lead up to the fight and while Williams dominated most of the fight he appeared content to just keep picking Botha off with punches rather than risk being hit trying to finish the South African off.

Having chosen such a dramatic step up in class to help him decide whether he had a future in boxing, Williams is unsure when he will step in the ring again to defend his WBA international heavyweight title.

"I think I am best at putting on the boots and running out on the field to play rugby union or rugby league," he said.

"If I had lost that fight I would have given it away because it is just not worth it but I overcame some hurdles and the reaction of all the people close to me was good so we will assess it when the time is right.

"For me boxing is a challenge. I am not perfect but I am just trying to keep improving and if everyone is saying I have improved then I will just keep plugging away and maybe have another fight.

"But at this stage I am concentrating on playing rugby league and we will assess that after the season. At this stage, I have had enough of boxing for now."